This invention relates to the facilitation of the isolation and subsequent analyses or molecules or compounds, particularly proteins in various biological and non-biological solutions through the use of a specially designed spin filter assembly comprising of a spin filter and a container closure means to separate proteins or other desired compounds after being bound to solid binding matrices or resins. Spin filters are also known as microcentrifuge tube filters.
A conventional spin filter is generally a tube having an open top end and a filter means on the bottom end opposite the top end. The spin filter is generally adapted to fit within the upper portion of a standard centrifuge holder, a microcentrifuge tube or a centrifuge cup. the usage of spin filters for separation are largely dictated by the type of filters attached or laid on top of the bottom end of the spin filter. Examples of filters currently used with commercially available spin filters are ion exchange membranes which typically separates the proteins, on the basis of their charges, from low molecular weight contaminants such as salts, detergents and others; membranes with pore sizes in the micrometer or nanometer ranges for removal of particles, concentration of proteins, for buffer exchange, reduction or removal of salts or other low molecular weight contaminants which includes among others, non-incorporated labels, linkers and primers. Affinity membranes, on the other hand, are used to capture specific proteins.
The use of microcentrifuge tube containing filters or spin filter, that selectively separate one component or compound from another is disclosed in U.S. Pat. No. 4,683,058. Different commercial manufacturers have adopted the concept and are selling variations of the microcentrifuge tube filters or spin filter either as a stand alone unit or as a component of an assay kit. None of the available spin filters, however, provide the desired recovery, ease and speed of separation that the spin filter assembly of this invention provides.
The spin filter assembly of this invention is key to facilitating the isolation and assay or test of a desired compound in solution because of the shortened separation time required for isolation and testing. The spin filter assembly of this invention comprise of a tube having an open top end, a bottom end opposite the open top end, a body of a first length, an inner diameter and a first outer diameter, a filter means at the bottom end, the tube insertable to an upper portion of a centrifuge holder having a closed lower end, an open upper end, a length longer than the first length of the tube, and a second inner diameter greater than the first outer diameter of the tube; and, a container closure means that fits on top of the open end of the tube. The filter means at the bottom end of the tube is preferably a woven screen of a desired mesh size or a second filtering media on top of the woven screen. The tube with the filter means is herein referred to as the spin filter. In the claims, the spin filter is referred to as the tube of the spin filter. The spin filter with the container closure means is herein referred to as the spin filter assembly which is the object of this invention. The spin filter assembly allow for multiple sample analysis and eliminates the transfer of one suspension or solution from one container to the other which is currently accomplished through the use of a transferring device such as a pipet. The filter means and the filtering media for protein determination and isolation is preferably a low protein binding filter. The filtering media used in this invention is of a particular porosity and geometry in the form of a filter frit that is applied on the bottom of the tube or on top of a woven screen which is attached to the bottom end of the spin filter. A filter frit as used herein means a flat filter disk typically and preferably made of porous plastic material. The geometry, porosity and depth of the filter frit of this invention allows for unimpeded flow with minimal liquid retention thereby allowing rapid separation, washing and elution steps commonly employed in various assay methodologies for organic compounds, more particularly proteins. The filter frit used herein allows for quantitative analysis of a desired compound or protein which is not necessarily achievable with other filtering media. Quantitative analysis means determining the concentration of a component or compound with accuracy. Due to the property of the filter frit of this invention, the number of steps needed for washing and elution is also reduced. Washing as used herein means adding a washing solution to a precipitate, a solid matrix, bead or pellet obtained after centrifugation to form a suspension and recentrifuging the suspension to reisolate the precipitate, solid matrix, bead or pellet. The washing step removes or recovers compounds in solution occluded within the solid precipitate, bead or pellet. Assay as used here is synonymous to the meaning of analysis, determination or test. The assay may be directed to the determination of the amount, size, and expression level of the desired compound and to detect presence of modification or degree of interaction of the desired compound with other compounds.
It is an object of this invention to provide a rapid procedure for isolating and subsequently analyzing the isolated protein or other desired compound in solution.
It is also an object of this invention to provide a spin filter assembly that shortens the analysis by reducing the time required for separating a liquid from a solid component.
It is also an object of this invention to provide a spin filter assembly that shortens the analysis by reducing or eliminating the transfer time of liquid or solid suspensions from one tube to the other.
It is also an object of this invention to provide a spin filter assembly that is adaptable for multiple sample processing.
It is also an object of this invention to provide a means for improving the accuracy of a determination, test or assay by reducing or eliminating device driven transfers from one container to the other and using a low binding filter media.
It is a further object of this invention to provide an analytical kit that is a complete system having the spin filter assembly as a component, for a fast and simple process of isolating and analyzing a desired compound.